One of the key components of a computer system is a place to store data. Typically computer systems employ a number of storage means, including "volumes" which can be disk drives (also called a direct access storage device or DASD), that are used to store data. Physical volume storage systems typically employ some number of physical volumes that each contains multiple tracks on which to store data.
An alternative to a physical volume storage system is a virtual volume storage system. A virtual storage system, such as a log-structure array system, typically contains a number of "virtual volumes," each having a "virtual track table" with pointers to "virtual tracks" on the virtual volume. The description of a virtual storage system is contained in IBM publication "IBM RAMAC Virtual Array" document no. SG24-4951-00 (IBM Copyright, 1997) which is incorporated herein by reference.
Both VSAM and non-VSAM data sets can be stored in a data storage system. Non-VSAM data sets differ from VSAM data sets in their organization and control information. The present invention is directed to maintenance of control information during data movement of non-VSAM data sets.
Data movement involves the copying and/or moving of a data set from one volume or set of volumes to another volume or set of volumes within a storage system. As the data set is copied or moved, the layout of the volumes within that storage system changes. However, even after a movement of the data set, the control information for the target data set that has been copied or moved must be maintained.
Unlike a physical volume environment, in a virtual volume environment the data set is not read into a host when the data set is moved. Within a virtual volume storage system, it becomes very difficult to maintain the control information when moving non-VSAM data sets that are not read into the host. Therefore, it becomes very difficult, or impossible, to determine the amount of data that actually resides on each volume after movement of non-VSAM data sets that are not read into a host computer.